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Push-Off

Started by DouginUtah, July 20, 2003, 11:15:32 AM

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DouginUtah

I really don't know if push-off is the right term to use for what I have experienced.
From The Suffolk Machinery troubleshooting web page:
1. BLADE RIDES UP IN THE CUT IN THE FIRST SIX INCHES AND STAYS THERE - it cuts straight until the end and then drops down. This is called "push-off." You have too much hook angle. Decrease the hook angle by 2 degrees.  See "HOOK ARTICULATION"
2. BLADE RIDES UP IN THE CUT - plus when you pull the board off you have a bow in the board. This is caused by too much hook angle and not enough set. Reduce the hook angle by 2 degrees and increase the set by .003" per side."

I have experienced this on my LT30: When I start the cut the blade rises up. If the guides are a 15" apart then the blade will be about 1/2"-3/4" higher than it should be. This forms an arc that stays up there until the end of the cut. This happened when cutting ash.

I have been told that I need to replace the power drive v-belts. This is true—they are worn out and I have already bought two new ones. But lets back up a minute to get the whole story.

I had cut a couple of hundred bd. ft. of the ash and was getting some build up on the blade. I got a spray bottle and water and started spraying the blade as I was cutting, and before starting the cut. Water didn't seem to "cut" it and the buildup increased. At this time I started to get push-off. In just a couple of passes it became severe. I shut it down and pondered the possibilities. I hadn't hit any metal (yet!). I considered the drive belts but they were in the same condition as just a few minutes earlier when I was getting a good cut. The blade tension was still at about 2200. So I figured the only thing that was changing was the blade. So, I took off the almost new blade and replaced it with a brand new, never used blade.

The push off immediately disappeared. I pumped the water (with a few drops of dish soap) more consistently and cut about 300 bd. ft. of ash and another 100 bd. ft. of walnut without any problems.

I have concluded that once you start getting build up on the blade your cut is going to get worse before it gets better! It was the condition of the blade, not hook angle which caused the push-off. Control the build up before it happens. Of course, my mickey- mouse spray bottle system would have been better if replaced by a proper drip/spray system.

-Doug
-Doug
When you hang around with good people, good things happen. -Darrell Waltrip

There is no need to say 'unleaded regular gas'. It's all unleaded. Just say 'regular gas'. It's not the 70s anymore. (At least that's what my wife tells me.)

---

Fla._Deadheader

I follow yer scenario. I have had the same thing happen, only, I have not had the build-up on the outside of the blade (opposite side from the wheels-tires).??? When I have the build-up, I believe the pitch and sawdust are mashed against the inside of the blade from contact with the tires-belts??? That would make the blade dive, not rise.
  Can you check the set on the blade that was arching??? We had that happen yesterday, then the blade broke, so, I can't really check the set???  I would like to know what you find.
  I cut mostly sticky SYP.
  I have checked Timberwolf blade set and found it off as much as .020 on a new blade. WM blade was shipped dull and would not cut??? Guess they all have problems???
   I just run a LOT of water on the blade and watch for the "yellow" streak of build-up, and scrape it with a putty knife as soon as I see it, before it starts diving.
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

LeeB

I get the same problem from a dull blade. LeeB
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

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